Preparation of substituted phosphinic nitrides



Sept. 23, 1958 c. s. FITZGERALD ETAL 2,853,517

PREPARATION OF SUBSTITUTED PHOSPHINIC NITRIDES Filed March 7, 1956DISSOLVE IN TETRACHLOROETHANE TREAT WITH NH4CI |2-2o HOURS |2o|socANHYDROUS CONDITIONS REMOVE AND- DISCARD ANY MATERIAL NOT IN SOLUTIONEVA PORATE SOLVE NT REDISSOLVE RESIDUE IN BENZENE RECRYSTALLIZE TOOBTAIN A FIRST CROP CONTAINING E s sI2 J AND A ssoowo CROP CONTAININGKC6H5)2PN PURIFY EACH CROP BY- FURTHER RECRYISTALLIZATION.

INVENTOR Char/es P. Haber Emil A. Lawton Camel/us G. FitzgeraldMai/@3204 QMTHMWJQW ATTORNEYS United States Patent PREPARATION OFSUBSTITUTED PHQSPHINIC NITRIDES Cornelius G. Fitzgerald, Ann Arbor,Mich., Charles P. Haber, Riverside, Calif., and Emil Abraham Lawton,Columbus, Ohio, assignors to the United States of America as representedby the Secretary of the Army Application March 7, 1956, Serial No.570,193

1 Claim. (Cl. 260-551) (Granted under Title 35, U. S. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor the Government for governmental purposes without the payment to usof any royalty thereon.

This invention relates to an improved method of preparing substitutedphosphinic nitrides. The method of the invention is more convenient andeconomical and gives higher yields than the previous method.

Polymeric disubstituted phosphinic nitridesmaterials of the form (RPN),, where R is a phenyl or other aryl groupare of increasing practicalinterest because they appear to offer exceptional thermal and chemicalstability at elevated temperatures. Previously, these products have beenmade by reactions of the appropriate Grignard reagent withphosphonitrilic chlorides. However, this old method is long and tedious,can be used only for relatively small batches, requires expensiveintermediates for the Grignard reagent, and gives extremely low yields.Indeed, the reported results of earlier workers using this method(Rosset, H., Compt. rendu 110, 750 (1925); Bode, H. and Thamer, R.,Ber., 76-, 121 (1943)) have been difficult to duplicate; the presentinventors know of In the old method (PNCI was prepared by the reactionof P01 and NH Cl. The crude (PNCl and (PNC12)4 then had to be purifiedby a tedious method. Finally, the purified material was reacted with theappropriate Grig-nard reagent to give (R PN) and (R PN) in extremely lowyields.

Other objects, aspects, uses, and advantages of the invention willbecome apparent from the following description and from the accompanyingdrawing.

The drawing is a flow chart showing the principal steps in a preferredpreparation of a disubstituted phosphinic nitride in accordance with themethod of the invention.

The following example of a particular preparation carried out by thepresent inventors will disclose and illustrate the practice of theinvention. (C H PCl is dis- "ice solved in anhydrous tetrachloroethaneor other suitable solvent, and a slight excess of anhydrous ammoniumchloride, NH Cl, is added. A temperature of from to 200 C., andpreferably between and C., is maintained for from 12 to 20 hours.Anhydrous conditions are maintained, and we believe that it is probablyalso desirable to exclude oxygen. Under these conditions the reactiontakes place.

Any material not in solution is then removed and discarded. The solventis removed by evaporation. The residue is redissolved in benzene, andthe benzene solution is extracted with dilute aqueous NaOH to removeunreacted (C H PCl and (C H POOH. We have also used petroleum ether,alcohol, carbon tetrachloride, and chloroform, instead of benzene.

Recrystallization from the benzene solution now gives a first crop thatis essentially the impure trimer,

and a second crop that is essentially the impure tetramer,

[(C H PN'] The later crops contain higher polymers of (C H PN andprobably other materials that have not been identified.

The impure trimer and the impure tetramer can be purified by a furtherrecrystallization of each. Combined yields of purified trimer andtetramer of about 10 percent are obtained, about half trimer and halftetramer.

It will be apparent to skilled chemists that (C H PCl;', is only anexample of a large number of compounds of the form R PX that can be usedas starting materials in the method of the invention. In this generalexpression, R can be any phenyl or other aryl group and X can be anyhalogen, provided only that the compound is not unstable under theconditions of the preparation.

We claim:

The method of preparing [(C H PN.],,, where n has values of three andfour, which method comprises: treatin (C H PCl With anhydrous ammoniumchloride in a solvent of anhydrous tetrachloroethane under anhydrousconditions at a temperature between 100 and 200 C.; evaporating thetetrachloroethane from the solution to obtain a residue of nonvolatilesolutes; redissolving said residue in benzene to obtain a secondsolution; extracting said second solution with a dilute aqueous solutionof sodium hydroxide to remove unreacted and (C H POOH from the secondsolution; and recrystallizing from said second solution to obtainReferences Cited in the file of this patent UNITED STATES PATENTS BrownMay 1, 1945 OTHER REFERENCES

